1. Field of the Invention
The present invention relates generally to a method for edge coating wood substrates and the resulting product. More specifically, the present invention relates to the coating of edges of wood substrates with a sprayable polyurea/polyurethane elastomer to produce a durable synthetic guard.
2. Description of the Prior Art
Wood substrates, including solid wood, and wood composites such as plywood, particle board, fiberboard, and the like have been used to provide flat horizontal surfaces for tables, countertops, chair seats, furniture tops, and other everyday surfaces for most of civilized history. One problem that has always accompanied their use is the wear and abuse that edges of these surfaces bear. For purposes of the present invention, an edge is defined as the exposed periphery bounded by a given substantially planar top surface and a substantially planar bottom surface. Edges may be flat, curved, or faceted.
Conventionally, the treatments of edges on these substrates has been predominantly the same as at least the top surface. Along these lines, if protection is to be afforded to an edge, shaped tops, such as those disclosed by U.S. Pat. No. 5,286,547 to Tyermann are typically used. This reference discloses the use of synthetic coating materials for the protection of an element of furniture, including edges. These coatings are applied to synthetic sheets which have been molded for a contour of the element, rather than directly applied to the edges, such that the portion of the coating which covers the edge of the underlying substrate is a continuous extension of the top. Though somewhat effective in providing protection to the substrate, these types of coatings are usually themselves not durable, since flowability and formability to various configurations are inherent in the materials chosen.
Prefabricated guards for the protection of edges are also known in the art. Typically, these are made of metal or plastics and must be attached to the edge, or to a portion of the top or bottom surface. Screws, nails, T-molds or adhesives are conventionally used. This type of edge guard has several disadvantages. The appearance of mechanical attachments detracts from the aesthetic appearance of the article made, whereas adhesive or T-molded attachments lack stability and durability. Further, premanufactured edge guards are limited to use on substrates of matching dimension.
Methods for applying coatings of polyurea/polyurethanes through spray application of amine/polyol-isocyanate reaction products have been the subject of earlier patents. For example, U.S. Pat. No. 5,266,671 to Primeaux, II discloses an abrasion resistant sprayable polyurea elastomer. These polyureas are the reaction products of isocyanates and amines applied under high pressure and temperatures. This patent reference additionally requires the use of a particulate filler. Similarly, EP 0420420 teaches a sprayable elastomer which may be either a polyurethane or a polyurea, but does not require fillers. Both disclosures are herein incorporated by reference. Neither reference discloses edge treatment of any substrate with polyureas. Further, these patents focus on increasing the flowability and moldability of polyurea/polyurethanes while maintaining the durable qualities of polyurea/polyurethanes. Accordingly, chain extenders, and in the case of U.S. Pat. No. 5,266,671, reinforcing fillers are used.
U.S. Pat. No. 4,009,307 to Erikson et al. discloses the use of isocyanate-terminated quasi prepolymers in the production of polyurea-polyurethane coatings. These coatings are taught to display excellent chemical and physical properties on wood substrates. These coatings may be optionally pigmented and spray applied. U.S. Pat. No. 4,663,201 discloses another polyurea coating which may be used on wood substrates. This patent requires the use of trifunctional isocyanates. U.S. Pat. No. 5,171,818 to Wilson discloses another sprayable polyurea-polyurethane coating which requires the use of aliphatic polyisocyanates. Again, no edge treatment is disclosed in any of these patents.
WO 86051795 to Turner et al. discloses the use of isocyanate-terminated quasi prepolymers in the production of polyureas. U.S. Pat. No. 5,160,766 to Waltrip et al. discloses a process for applying a coating composition at high temperatures (65-120 degrees F.) and pressures (about 2,750 psi). The spray process produces a coating for various substrates, though wood is preferred. This reference does not specifically teach the use of polyurea/polyurethanes, nor does it teach any edge treatment.
None of the above inventions and patents, herein incorporated by reference, taken either singly or in combination, is seen to describe the instant invention as claimed.